This application relates generally to gas turbine engines and, more particularly, to a method and apparatus for identifying when gas turbine fan blade damage has occurred.
Gas turbine engines typically include high and low pressure compressors, a combustor, and at least one turbine. The compressors compress air which is mixed with fuel and channeled to the combustor. The mixture is then ignited for generating hot combustion gases, and the combustion gases are channeled to the turbine which extracts energy from the combustion gases for powering the compressor, as well as producing useful work to propel an aircraft in flight or to power a load, such as an electrical generator.
At least one known gas turbine fan assembly includes a plurality of rotor blades each having an airfoil that is fabricated utilizing a metallic material, such as titanium for example, and a composite material that is bonded to the surface of the airfoil. More specifically, the known airfoil is fabricated such that the composite material is laid up as individual unidirectional plies of material on the surface of the airfoil.
During operation, foreign objects may be ingested into the engine. More specifically, if a foreign object strikes the fan airfoil, a portion of the composite material may be liberated from the airfoil and thus enter the engine flow path resulting in further foreign object damage to the gas turbine engine the foreign object cause the fan blade to bend or lean slightly resulting in increased vibration.
At least one known method of determining whether a foreign object has damaged an airfoil includes manually inspecting the gas turbine engine during scheduled maintenance periods. Another known method of determining whether a foreign object has impacted a rotor blade includes installing a vibration sensor within the gas turbine engine to monitor the vibration level of the gas turbine engine during operation. More specifically, during operation, vibration data is collected from the gas turbine engine during a plurality of flights, for example. The vibration data accumulated vibration data is then downloaded during a maintenance event and analyzed to determine whether an object has impacted a fan blade.
However, while both above described methods are effective in determining when an object has impacted an airfoil, each method is relatively time consuming thus facilitating an increase in the maintenance costs. For example, while manually inspecting the gas turbine engine to identify damaged fan blades is effective, the procedure generally is relatively time consuming. Moreover, while utilizing the vibration data to identify damaged fan blades is also effective, known algorithms require a plurality of data that is collected over an extended period generally including a plurality of flights. The accumulated data is then analyzed during a maintenance period to identify potentially damaged fan blades. As a result, damaged fan blades may not be detected until the next maintenance event.